The present invention relates generally to operations performed in conjunction with a subterranean well and, in an embodiment described herein, more particularly provides a method whereby a latch profile is installed in a tubular string.
It is common practice to set a packer (or another anchoring device, such as a liner hanger or hanger/packer) in a casing string in a parent wellbore prior to drilling a branch wellbore. The packer provides a secure platform to which a whipstock may be attached during the processes of milling through the casing and drilling the branch wellbore. The packer also seals against the casing, which may be used to provide pressure isolation for a zone of the parent wellbore below the intersection with the branch wellbore, or which may aid in preventing debris from falling down in the parent wellbore.
Various types of packers have been used for this purposexe2x80x94permanent packers, retrievable packers, hydraulically set packers, mechanically set packers, etc. Nevertheless, all of these various types of packers share a common disadvantage in that they restrict access and flow through the parent wellbore. If full bore access to the parent wellbore below the branch wellbore intersection is desired after the branch wellbore is drilled, the packer must be unset and retrieved from the well (which is many times quite difficult to accomplish), or the packer must be milled through or washed over (which is quite time-consuming).
Because of this wellbore restriction due to the use of packers in multilateral wellbore drilling, multilateral wells are typically constructed from bottom up. That is, a first branch wellbore is drilled from a parent wellbore, then a second branch wellbore is drilled from the parent wellbore at a location above the intersection between the parent and first branch wellbores, then a third branch wellbore is drilled from the parent wellbore at a location above the intersection between the parent and second branch wellbores, etc. This situation unnecessarily limits the options available to the operator, such as to drill the branch wellbores in another, more advantageous, sequence or to drill a previously unplanned branch wellbore below another branch wellbore, etc.
In addition, a packer relies on a gripping engagement with the casing using slips. This gripping engagement may fail due to the severe forces generated in the milling and drilling operations. Such gripping engagement also provides limited radial orientation of the packer relative to the casing, so if the gripping engagement is ever relieved (such as, by unsetting the packer), any subsequent radial orientation relative to the casing (for example, to re-enter the branch wellbore) will not be able to benefit from the original orientation of the packer.
In carrying out the principles of the present invention, in accordance with an embodiment thereof, a method is provided in which a latch profile is installed in a tubular string after the tubular string is positioned in a well. The method permits an apparatus such as a whipstock to be secured in the tubular string. The latch profile may provide for radial orientation of the apparatus.
In one aspect of the invention, the latch profile is formed on an expandable latch structure which is conveyed into the tubular string. The latch structure is then expanded outward, thereby securing the latch profile to the tubular string. For example, the latch structure may deform the tubular string when it is expanded outward, thereby recessing the latch structure into an interior surface of the tubular string and leaving full bore access through the tubular string. Bonding agents, such as adhesives and sealants may be used to bond the latch structure to the tubular string.
In another aspect of the invention, the latch profile may be formed on the interior surface of the tubular string by creating recesses on the interior surface. The recesses may be formed in a predetermined pattern, so that an apparatus engaged therewith will be secured relative to the tubular string and radially oriented relative to the tubular string.
In yet another aspect of the invention, the latch profile may be formed on the interior surface of the tubular string by cutting into the interior surface to create the recesses. For example, cutting tools such as drills or mills may be used. If the recesses extend through a sidewall of the tubular string, thereby forming openings through the sidewall, sealant may be injected into the openings to prevent fluid flow therethrough.
In still another aspect of the invention, the latch profile may be installed in the tubular string using any of the methods summarized above, and then an apparatus may be operatively engaged with the profile in a single trip into the well. This may be accomplished by attaching the apparatus to a latch profile installation assembly and conveying these together into the well.
These and other features, advantages, benefits and objects of the present invention will become apparent to one of ordinary skill in the art upon careful consideration of the detailed description of a representative embodiment of the invention hereinbelow and the accompanying drawings.